Nemmi, did you wash your Issy bear inserts in hot a few times before using it? I have found that they take quite a few washes to get to full absorbency. Mine last easy 3 hours for day and 11 at night.
Back to the topic. I have my little ripple as stash fillers and they work well for me. Mine have had a lot of use over about a year and the PUL is delaminating on most of them now but they still don't leak. I wouldn't use them with just the one microfibre insert though. I add bamboo or another two layer microfibre insert. They are good value for money IMO to bulk out the stash and also let DS loose in them in summer wearing just a nappy when I don't want my good ones wrecked.